Some names of animals are more often written in katakana than kanji, there seems to be no hard and fast rules, except where the name is taken from a foreign language such as lion (rion リオン), where the word is written in katakana.

There are some interesting compounds such as goat as "mountain sheep", hedghog as "needle-mouse" (harinezumi) and dolphin as "sea pig." Animals are also common in Japanese place names such as Kumamoto (熊本) in Kyushu and Tsuruhashi (鶴橋) in Osaka.

Expressions using animals are common in Japanese and the book Japanese Proverbs and Sayings by Daniel Crump Buchanan has a number of proverbs dedicated to animals. Perhaps the most famous is: saru mo ki kara ochiru 猿も木から落ちる - meaning everyone can make a mistake. One not heard so much nowadays is neko ni koban 猫に小判 (lit. 'gold coins to a cat' so casting pearls to swine).